Test circuit



March 26, 194s.

P. N.BURRows Erm.

'TEST CIRCUIT Filed Feb. 1o; 1942 P/fcy M MTQRNEY Patented Mar. 26! 1946 TEST CIRCU'E Percy N. Burrows, St. Albans, and Norman Lockwood, Flushing, N. Y., signora to Smirnoff-x Vacuum Oil Company, Incorporated, New orlr, N. Y., a corporation of New Yori:

Application February 16, 3.942, Serial r2. C. miie-329? 2 Gleims.

This invention relates to an electrical circuit including e. condition responsive element together with means for timing the duration of a desired condition and means actuated thereby to operate suitable controls in the event the desired condition is of improper duration. Specifically, the invention is concerned with a purge timing relay or means for determining whether e. :Flow ci' gas is of sumcient duration and space velocity end for insuring that no deleterious results shell follow insuhcient gas flow.

ln a specific embodiment in which the apparatus o1 this invention has been employed, itis associated with electrical controls of a plant for the catalytic cracking of heavy hydrocarbon oils to lighter products such as gasoline. A granular catalyst is disposed in each of a plurality of closed vessels, hereinafter called casesf provided with means to supply and withdraw fluid products. The cases are also equipped with heat exchange elements having no bearing on the present invention.

rEhe granular catalyst is such that, after operation on-stream, that is, passing oil vapor therethrough for treatment, for a certain period of time, the catalyst becomes contaminated with carbonaceous by-products of the treating operation to such an extent that its efficiency is seriously reduced. A pre-heated oxidizing gas, such as air, is then passed through the catalyst to burn oi the deposits of carbonaceous matter and restore the elciency of the catalyst. This step is known as regeneration. In commercial operation, several cases, usually in groups of three, are operated simultaneously in order that a continuous stream of vhydrocarbon vapors may be supplied to the battery of cases and regeneration in one will be concurrent with an ori-stream period of at least one other, the cases each operating on a predetermined cycle of alternate on-stream and regeneration periods. In a typical installation, a complete cycle occupies e. period of about 4G minutes.

As will be readily apparent, great caution must be exercised to avoid formation of explosive mixtures in the cases (which operate at temperatures upwards of 750 F.) when changing from onstream to regeneration and vice versa. This is generally accomplished by e, step of purging with inert gas such as steam at each change-over, with or without an additional purging by application of a vacuum to the case. Obviously, it is of greatest importance that the purging be of an extent not less than a minimum which will render the atmosphere in the case inert to the maonV terlal to he introduced. @dany knovm means have eeen tried to lnsrne that the steam purging, or purging with other inert ges such as products of combustion. snail ce conducted with e. minimum space velocity ci medium for a minimum period of rione of the known devices has proven satisfactory and. we have developed a novel reiay controlled circuit to accomplish that pur pose.

The specinc novel circuit or the invention illustrated here is designed for use connection with the present electrical controle on catalytic cracklng plants. ln the particular installation for which the specific circuit described was designed, operation of the plant is by Ineens o automatic electrical controls. cattery or? three cases are operated hy a master cycle timer or the Eli-5 and types described in the General Electric Bulletin @EG-2533 which comprises a plm-eilt;J of successive conductive segments connected to electrical operating equipment and e contacting element moving over and successively energizing the segments. dach of the valves for controlling conduits to supply and withdraw hydrocarbon vapors, regenerating air, purging medium, etc., 'to each cese, is operated by an electric motor placed operatic-n 'through a suitable relay enerrom the cycle timer. Associated with each valve there is also a test contact which opens when the valve reaches an extreme position, either open or closed. 011e segment, spaced to provide e. suitable time interval after each valve operating segment is connected for supplying e. test current to seid test contact. Suitable relays are provided to shut down the battery in the event the test current iov-rs, indicating an improperly operated vaive.

The circuit of the present invention provides metering Ineens for determining Whether the purge gas flow is equal to or greater than a predetermined mnimum both in space velocity and time oi now. Means are provided responsive to said metering ineens for preventing valve operation in the battery and for setting in operation the alarm and shutdown mechanisms of the cycle timer in the event these minima are not met.

The nature or the invention will be apparent from the following description when considered in connection with the annexed drawing, `wherein:

Figure l is a schematic wiring diagram of a specific embodiment of the invention; and

' Figure 2 is a diagrammatic elevation of one face of the purge timing relay.

The form of the invention illustrated in Figure may be mounted on arms Il as shown in Figure i and held in adjusted position as shown in Figure 2 by means o! washer 35 and nut 3B. One of the permanent magnets as shown in Figure l in back of the disk I3 may be ilxed without affecting adjustability as will be apparent.

Preferably, signal lamps 30 and 31 are also ineluded to indicate the state of the device. Green light 3l is connected in parallel with motor il' and will be illuminated when said motor is operating. Amber light is in a circuit completed through poles 2' and i" oi' the test and A relays, respectively, Illumination of this light indicates that a purge has been satisfactorily completed and that the test impulse through line I3 from the cycle timer will not be followed by alarm and shut-down of the battery.

We claim:

i. In a device of the class described, a substantially constant speed motor, a motor circuit ior supplying an energizing current to said motor, a normally open switch in said motor circuit adapted to close responsive to a predetermined minimum iiow of iiuid in a conduit, means to energize said motor circuit, a test circuit, means to apply an electrical impulse to said test circuit at a iirst predetermined interval of time after said motor circuit is energized, a circuit breaker in said circuit and means responsive to the rotation of said motor to open said circuit breaker following operation of said motor for a second predetermined interval of time; whereby said test circuit is conditioned to indicate satisfactory operation only if the flow of fluid has been at a rate not less than said minimum for a period oi' time equal to said second predetermined interval during said first predetermined interval.

2. In an apparatus for control of a process requiring flow oi.' a uid at not less than a predetermined minimum rate for not less than a predetermined minimum time oi' ow and having a test circuit and means to apply an electrical impulse to said test circuit at a predetermined test interval oi time after said ow of fluid is initiated; the combinationr with said control apparatus of a substantially constant speed motor, a motor circuit for supplying an energizing current to said motor, a normally open switch in said motor circuit adapted to close responsive to said predetermined minimum rate of flow of said uid in a conduit. means to energize said motor circuit, means responsive to rotation of said motor to condition said test circuit upon rotation of said motor for a period o! time equal to said predetermined minimum time.

PERCY N. BURROWS, NORMAN R. LOCKWOOD. 

